1. Field of the Invention
The subject invention relates to adjuvants for postemergent herbicides, which fall into the category of crop oil concentrates. More particularly, the subject invention relates to improved crop oil concentrates which enhance the efficacy of herbicides, allowing greater or equal weed control while using less active ingredient, while being capable of being mixed with the herbicidal active ingredient to form a storage stable, self-emulsifying, ready-to-dilute (RTD) formulation.
2. Description of the Related Art
It is well established that a variety of adjuvants play important roles in the application of herbicides. These adjuvants are a diverse group of components with equally diverse functions which may often be determined from their generic names, i.e. "spreaders," "stickers," "solubilizers," "emulsifiers," "flow control agents," "drift control agents," and so on. Among the many useful herbicide adjuvants are the so-called "crop oil concentrates."
Crop oil concentrates are often recommended by herbicide manufacturers and formulators for inclusion in tank mixes to increase the efficacy of postemergent herbicide formulations. Crop oil concentrates are available from a variety of sources, and generally consist of from 75-95 percent by weight of a hydrocarbon oil or solvent with the balance being a surfactant, although in certain cases the surfactant may comprise a majority of the composition, or even all of the composition.
The hydrocarbons which form a major part of the crop oil concentrate may be derived from mineral (petroleum) or vegetable sources. When derived from mineral sources, the hydrocarbon component may be predominantly paraffinic, or may be aromatic, particularly alkylated aromatic.
Although the use of selected crop oil concentrates may enhance herbicidal efficacy, it is well known that many of the proprietary concentrates available are not as effective as others. Some may even impact negatively upon herbicidal efficacy. Additionally, there is a great deal of inconsistency with regard to the composition of available crop oil concentrates, complicated by the fact that manufacturers frequently change formulations without notifying the consumer, resulting in a great deal of uncertainty with regard to their performance.
In recent years herbicide/crop oil premixes have become commercially desirable products. Thus rather than having to prepare a tank mix from separate herbicide and crop oil containers, it would be desirable to prepare herbicides and crop oils in one formulation which is ready to dilute. Such RTD formulations present further problems. For example, the presence of active chemical species in the formulation may cause decomposition of the active ingredient, and thus the storage life of the formulation may be unduly limited. Moreover, the formulation must be freeze thaw stable, and should in addition be self-emulsifying when added to the application tank. Finally, the result emulsion or dispersion should be stable over at least a half hour to several hours under moderate agitation.
One commercial sethoxydim ready-to-dilute formulation, NABU-S, a product of Nippon Soda, utilizes polyoxyethylated fatty acid and a sorbitan fatty acid ester as emulsifiers in an amount of about 26 weight percent along with about 61.5 weight percent of machine oil. However, this formulation loses approximately 25 percent of its activity after only 3 months storage at 50.degree. C., and is not particularly effective at enhancing sethoxydim activity.
In copending U.S. application Ser. No. 104,658 are disclosed crop oil concentrates which not only are highly effective with a broad spectrum of individual herbicides, but also unexpectedly decrease the apparent antagonism often exhibited when two or more herbicides are used together. These crop oils contain an aromatic or paraffinic solvent or diluent, a fatty acid, one or more lower alkyl fatty acid esters, and a particular group of anionic surfactants which are polyoxyalkylene sulfates, phosphates, or carboxylates. Unfortunately, this highly effective crop oil concentrate, when added to cyclohexenone herbicides to prepare a ready-to-dilute formulation, causes rapid degradation of the active ingredient, and thus its use must be restricted to tank mixes prepared from individual herbicides and crop oils.
Copending U.S. application Ser. No. 237,609 disclosed crop oil adjuvants which, while not especially effective in avoiding herbicide antagonism, nevertheless are very effective crop oils, especially with cyclohexenone herbicides. However, once again, when combined with the active herbicidal cyclohexenone in a ready-to-dilute formulation, considerable decomposition of the active ingredient occurs.